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A favorable combination of sensitive area and viewing time for the UCSD/MIT Hard X-Ray and Gamma-Ray Telescope on satellite HEAO-1 permitted significant contributions to the study of binary systems. Results are reviewed for five fast pulsars: Her X-1, 4U0115+63, LMC X-4, SMC X-1 and Cen X-3.
Be star binaries with neutron star companions are shown to constitute a major class of X-ray sources. Some general observational and interpretive techniques of X-ray astronomy are reviewed. Data for 12 Be/X-ray binary systems are summarized. The Be/X-ray binaries are found to be systematically wider systems, with lower-mass primaries, and with significantly more transient behavior than the 'standard' massive X-ray binaries such as Cen X-3 and SMC X-1. The difference between the two types of X-ray binaries is explained in the context of slightly different evolutionary scenarios for the progenitor binaries. The 'standard' massive X-ray binaries result from wind-mass-loss dominated evolution of very massive close binaries, while Be/X-ray binaries probably result from mass-transfer dominated evolution of systems with primary masses less than approximately 20 solar masses. The implications of the X-ray observations of Be/X-ray binaries for Be stars in general are discussed.
The results of Einstein Observatory studies of X-ray emission from normal galaxies, including the LMC and SMC, M31, M33, M101, NGC 247, M81 and M100, and N253 are surveyed. The X-ray luminosity of normal galaxies is proportional to their optical luminosity, revealing no strong dependence on galaxy type. The number of individual sources detected are comparable to the number of sources expected on mass considerations. There are substantial numbers of X-ray sources in the Magellanic Clouds with luminosities in the range 10 to the 35th-36th ergs/s, lower than most X-ray binaries but higher than known uncollapsed stellar systems. About seven X-ray sources with luminosities of at least 10 to the 39th ergs/s in the 0.5-3.0 keV band have been found in the arms of nearby spiral galaxies.
High-resolution IUE spectra of Sk 160, the optical counterpart of the X-ray source SMC X-1, show substantial variations with orbital phase of the resonance P Cygni profiles. These variations are ascribed to the changing ionization state in the stellar wind caused by the X-rays emitted by the companion, as suggested by Hatchett and McCray and first established for the galactic X-ray binary Vela X-1. Furthermore, the profile observed during X-ray eclipse differs significantly from profiles of similar stars in the absence of X-ray ionization.
The support of previous SAS 3 spacecraft observations by new data gathered by the Monitor Proportional Counter aboard the HEAO 2 spacecraft indicates that the pulse period history of the 13.5 sec-pulsing X-ray source LMC X-4 is consistent with standard accretion and torque models only if LMC X-4 is a fast rotator for which the accretion torques nearly cancel. This result leads to a neutron star magnetic field strength estimate of about 1.2 x 10 to the 13th G. Strong evidence is noted for Her X-1's status as a fast rotator, while SMC X-1 is probably an intermediate-to-fast rotator. In the context of slaved disk models for these objects, it is noted that the precession periods expected for the companion stars are significantly longer than the observed 1-2 month time scales; slaved disk models are thereby undermined.
O and B stars in the LMC and SMC have been observed with the IUE in order to compare their winds and mass loss rates with those of their galactic counterparts. It is found that while the wind terminal velocities are generally about 20 percent lower than in galactic stars of the same spectral type, it is not clear that the mass loss rates are significantly lower. This conclusion differs from the conclusions of other studies, and the reasons are discussed. The most important reason is that a less luminous set of stars with new spectral types determined from slit spectra is being examined. The discussion of stellar winds rests heavily on a comparison of relevant wind parameters observed in O stars using both high and low dispersion IUE spectra.
Preliminary results are reported for an investigation comparing theoretical models of the sudden appearance of an extended RGB (and its effects on the spectral energy distributions of stellar populations) with data from ESO CCD observations of clusters in the LMC and SMC. Isochrones for the entire RGB are being constructed on the basis of 100 new evolutionary sequences (calculated using the evolution code of Sweigart and Gross, 1976 and 1978) to permit determination of synthetic colors and spectral energy distributions. The observations so far indicate a main sequence about 0.1 mag redder than that predicted by the present models or by the isochrones of VandenBerg and Bell (1985), and fail to show a B-V color difference at the RGB phase transition.
Local-area network (LAN) for computers prevents single-point failure from interrupting communication between nodes of network. Includes two complete cables, LAN 1 and LAN 2. Microprocessor-based slave switches link cables to network-node devices as work stations, print servers, and file servers. Slave switches respond to commands from master switch, connecting nodes to two cable networks or disconnecting them so they are completely isolated. System monitor and control computer (SMC) acts as gateway, allowing nodes on either cable to communicate with each other and ensuring that LAN 1 and LAN 2 are fully used when functioning properly. Network monitors and controls itself, automatically routes traffic for efficient use of resources, and isolates and corrects its own faults, with potential dramatic reduction in time out of service.
High-resolution spectra of SN 1987A obtained with the IUE satellite show absorption features from the disk and halo of the Galaxy and the LMC. A rich variety of elements and ionization states is found, including allowed resonance lines of abundant elements with ionization states ranging from C I and O I to Al III, Si IV, and C IV. The Si IV and C IV absorption at LMC velocities is unusually strong toward the supernova as compared to most other stars in the LMC and SMC. The origin of these lines is discussed.
The atlas contains a homogeneous set of optical spectrophotometric observations (3300-7300 A) at moderate resolution (about 10 A) of almost all WC and WO stars in the Galaxy, the LMC, and the SMC. The data are presented in the form of spectral tracings (in magnitude units) arranged by subtype, with no correction for interstellar reddening. A montage of prototype stars of each spectral class is also shown. Comprehensive line identifications are given for the optical lines of WC and WO spectra, with major contributions tabulated and unidentified lines noted.
In the HEAO 1 A-2 survey of fast X-ray transients, a search of 2 to 20 keV scanning data was made for brief increases in flux, greater than 4 millicrabs, on timescales approximately 1 to 10 to the 4th s above a 12-hour average. The search was divided into two regions, and all-sky survey of the Galaxy, and a survey of the Magellanic Clouds. In the latter, 37 events were found and identified with 4 of the 5 brighest sources in the LMC, plus 2 as flares from a foreground star. Np X-ray bursts, no gamma-ray bursts, and no events from the SMC were found. In the all-sky survey, after excluding well-known variable sources, out of the equivalent of approximately 104 days of data, 15 events were found which falling into 2 broad categories: flares from coronal sources, roughly isotropically distributed, with optically thin thermal spectra; and harder fast transients apparently distributed near the Galactic plane. The first were identified as flares from ubiquitous active cool dwarf stars. It was hypothesized that the second may have been from distant Be-neutron star binaries. However, at least two of the harder, more luminous events remained unidentified. Future research should examine the nature of these rare events, and how they may fit into a hierarchy of hard fast transients from gamma-ray bursts to outbursts from pulsar systems.
Fiber-reinforced composite laminates are used in many aerospace and automobile applications. The magnitudes and durations of the cure temperature and the cure pressure applied during the curing process have significant consequences for the performance of the finished product. The objective of this study is to exploit the potential of applying the optimization technique to the cure cycle design. Using the compression molding of a filled polyester sheet molding compound (SMC) as an example, a unified Computer Aided Design (CAD) methodology, consisting of three uncoupled modules, (i.e., optimization, analysis and sensitivity calculations), is developed to systematically generate optimal cure cycle designs. Various optimization formulations for the cure cycle design are investigated. The uniformities in the distributions of the temperature and the degree with those resulting from conventional isothermal processing conditions with pre-warmed platens. Recommendations with regards to further research in the computerization of the cure cycle design are also addressed.
Application of the Baade-Wesselink method to three field RR Lyrae variables reveals evidence of shock waves in the atmospheres of RV Phe and V440 Sgr (but not YZ Cap) during maximum light. The results yield distance moduli of 24.21 + or - 0.20 for M31, 18.26 + or - 0.20 for the LMC, and 18.85 + or - 0.20 for the SMC. Using the Sandage (1982) age/turn-off luminosity relationship of VandenBerg and Bell (1985), estimated ages of 18.8 Gyr for M92 and of 15.7 Gyr for 47 Tuc are derived.
Ultraviolet and optical spectra data are presented for the oxygen-rich supernova remnant 1E 0102-7219 in the SMC. These UV data are the first to seriously constrain the UV emission from an oxygen-rich remnant. Emission lines of O I, forbidden O II, semiforbidden O III, semiforbidden O IV, C IV, forbidden Ne IV, and Mg II have been unambiguously detected in the UV. Shock models for material with abundances appropriate to massive stellar ejecta are calculated, and a number of differences between these models and the observations are found. The UV lines are observed to be weaker relative to optical lines than expected from models. Models of photoionization by the remnant's X-ray emission are calculated, and these provide a better qualitative match to the observed spectra. Approximate abundances in the ejecta are derived and the implications these have for the precursor star are discussed.
Low resolution IUE observations of the dwarf elliptical galaxy NGC 205 show that the UV spectral energy distribution (SED) of the galaxy is relatively flat. Spectra centered on the nucleus and on a region north of the nucleus show evidence of recent bursts of star formation which contribute strongly to the UV spectral energy distribution. The UV spectra was fit with a composite spectrum based on a Miller-Scalo initial mass function, an underlying older population (modelled using the UV spectrum of 47 Tuc), and an extinction based on a SMC-like extinction cure. This fit implies that the total mass of young stars (with M equal to or greater than 1 solar mass) in the galaxy is approx. 7x10(5) solar mass, which can be compared to the total mass of globular cluster like stars in the galaxy of approx. 8x10(7) solar mass.
An optical and ultraviolet study is presented of object 28 of Sanduleak et al. (1978) in the SMC. This object is an extreme type of I PN which apparently has undergone all three stages of nuclear dredge-up together with an appreciable amount of convective envelope burning. Optical and UV data are well-represented by a model in which the central star has a temperature of 180,000 K and a radius of 0.09 solar radius. A nebular mass of 0.71 solar mass and a central star mass of 0.65-0.71 solar mass are inferred. The object apparently evolved from a massive progenitor with main-sequence mass greater than five solar masses, which underwent both second and third nuclear dredge-up and very efficient hot bottom burning.
Low-resolution IUE observations of the dwarf elliptical galaxy NGC 205 show that the UV spectral energy distribution of the galaxy is relatively flat. Spectra centered on the nucleus and on a region north of the nucleus show evidence of recent 'bursts' of star formation which contribute strongly to the UV spectral energy distribution. The UV spectra are fit with a composite spectrum based on a Miller-Scalo initial mass function, an underlying older population and an extinction based on a SMC-like extinction curve. This fit implies that the total mass of young stars in the galaxy is about 700,000 solar mass, which can be compared to the total mass of Population II stars in the galaxy of about 100 million solar mass.
The Roentgen international x ray observatory on the Kvant module of the Mir space station has been successfully operating since the beginning of June 1987. Many x ray sources were observed and among them were several x ray pulsars. Four telescopes mounted on board the Kvant module cover a wide energy range with good timing resolution. Timing analysis of the Kvant module data suffers from the presence of only short continuous intervals of source observations, separated by 90 min gaps (90 min is the orbital period of the Mir space station around the Earth). The presence of 90 min gaps leads to the appearance of beat frequencies v=v sub 0 + or - n/90 min (n = 1, 2, 3). Special analysis was applied to avoid this difficulty. Results are presented of the pulsation period measurements of the x ray pulsars Her X-1, Cen X-3, SMC X-1, Vela X-1, A0535 + 26 by the instruments on board the Kvant module in 1987 to 1989. The values of the periods are reduced to the solar system barycenter and to the binary system barycenter (excluding A0535 + 26).